The ability to tailor the charge on cellulose-rich fibers is central to converting this important bioresource into high-end materials. However, increasing the charge often compromises the nanostructural integrity, leading to partial dissolution at high substitution levels. This work presents a new synthetic strategy for enabling cellulose-rich fibers with high and tunable charge densities (1.4–6.7 mmol/g). The method relies on radical transfer grafting via to and from polymerization of acrylic acid from thiolated fibers in water, with detailed analysis of each reaction step and how the surrounding system influences radical transfer. The resulting approach unites free radical polymerization with biopolymer science in a highly direct and versatile manner. We further show that the charged fibers perform exceptionally well in water remediation, reaching uptake values comparable to or exceeding state-of-the-art metal-organic framework (MOF) materials. This strategy offers a practical foundation for creating next-generation bio-based materials with tailored functions.

Barriers in the human body play a crucial role in regulating the exchange of substances between compartments, with permeability alterations occurring under both physiological and pathological conditions. In vitro barrier models are essential tools for studying the mechanisms of molecular diffusion across these barriers. Traditional coculture systems or advanced organ-on-chip (OoC) platforms mostly utilize permeable membranes based on artificial, nonbiodegradable materials. In this study, we introduced cellulose nanofibrils (CNFs)-based membranes to develop a new class of in vitro barrier systems. CNFs, derived from natural sources, are nontoxic, biodegradable, optically transparent, and feature a 3D fibrillar structure that mimics the cellular basement membrane. We successfully modulated the permeability of CNF-based membranes, interposed in dual-chamber polydimethylsiloxane devices, to small molecules through chemical and enzymatic treatments, while preserving their ability to allow cell adhesion and growth. This technology holds potential for its integration in next-generation OoC devices, offering more realistic and complex models that closely mimic the physiological behavior of human barriers.

Superabsorbent polymers (SAPs) are essential components in absorption products for food packaging, agriculture, wound dressings, and hygiene. Modern absorption products are designed to rapidly absorb and transport liquids to SAPs, which drains the porous networks and hold liquids under pressure as hydrogels. However, the carbon footprint of these massively used, fossil-based products is high, leading to an urgent need to develop biobased superabsorbents. Although commercial SAPs have an absorption capacity under load that is challenging to surmount, their powder form complicates processing. Thus, biobased alternatives can compete with other advantages, such as intelligently designed self-supporting structures preferably manufactured in sustainable roll-to-roll processes. As a pioneering step, this study presents all-cellulose superabsorbent heterostructures prepared by combining macroporous fiber-based aerogels with highly swelling cellulose nanofibril (CNF) sheets. The aerogel rapidly absorbs 30 g g-1 of liquid, which is rapidly transferred to the CNF sheets with a maximum capacity of 246 g g-1, holding liquids at pressures of up to 0.9 MPa. The heterostructure is also equipped with a simple, sustainable conductometric water-uptake sensor to follow the liquid uptake and saturation level. Using unmodified raw materials from the forest industry in a scalable process with the potential for roll-to-roll manufacturing makes these all-cellulose heterostructures a competitive alternative to commercial SAPs in a carbon-neutral society.

Biobased cellulose nanofibrils (CNFs) constitute important building blocks for biomimetic, nanostructured materials, and considerable potential exists in their hybridization with tailorable polymeric nanoparticles. CNFs naturally assemble into oriented, fibrillar structures in their cross-section. This work shows that polymeric nanoparticle additives have the potential to increase or decrease orientation of these cellulose structures, which allows the control of bulk mechanical properties. Small amounts of these additives (<1 wt%) are shown to promote the alignment of CNFs, and the particle size is found to determine a tailorable maximum feature size which can be modified. Herein, X-ray scattering allows for the quantification of orientation at different length scales. This newly developed method of measuring cross-sectional orientation allows for understanding the influence of nanoparticle characteristics on the CNF network structure at different length scales in hybrid cellulose-nanoparticle materials, where previously quantitative description has been lacking. It thus constitutes an important foundation for further development and understanding of nanocellulose materials on the level of their nanoscale building blocks and their interactions, which in turn are decisive for their macroscopic properties.

Quaternized cellulose fibers and cellulose nanofibrils (CNFs) are attractive candidates for the development of new renewable and biodegradable materials. However, the etherification reaction, through which functionalization is commonly achieved, provides low efficiencies, limiting industrial interest in the modification. This work primarily aims to increase the efficiency for the quaternization of cellulosic fibers while keeping the fiber-structure intact. This was achieved using high-consistency kneading to mix and modify the fibers at far higher solids contents than previously reported, efficiently limiting the alkaline hydrolysis of the reagent. Increasing the solids content from 5 to 45 wt% improved the reaction efficiency from 2 % to unprecedented 38 %. Characterization of the fibers showed that high-consistency quaternization affected the wet dimensions of the fibers, with enhanced swelling and fibrillation being obtained. Based on the tensile testing of handsheets made, it was concluded that quaternizing the fibers enhanced the strainability of the material, from 1.8 to 6.7 %, and that kneading achieved a concomitant increase in stress-at-break, from 15 to 103 MPa. CNFs produced from fluidized high-consistency-quaternized fibers had dimensions comparable to those produced from hand-mixed fibers, having aspect ratios above 200, the CNF films produced were transparent, tough, and with a high propensity to sorb water.

Due to their excellent wetting and liquid-spreading properties, cellulose-based aerogels have shown great potential as absorbent materials in many applications. However, there is still a very limited understanding of how the aerogels should be tailored to optimize liquid spreading and liquid storage properties. The present work focuses on characterizing liquid spreading at short contact times and tailoring the surfaces within the aerogel to increase the spreading properties. Aerogels from periodate oxidized cellulose nano fibrils (CNFs) were freeze-linked to attain wet stability. Subsequently, they were modified with the layer-by-layer (LbL) assembly method using poly(diallyldimethylammonium chloride) (PDADMAC) and well-defined SiO2 nanoparticles to change their surface properties. The morphology of the untreated and treated aerogels, as determined from SEM images, indicates a complete surface coverage of PDADMAC/SiO2 bilayers on the inner surfaces of CNF aerogels, showing that the LbL-treatment can be used to tailor the aerogel, i.e. to increase the specific surface area of the aerogel, by changing the number of bilayers. It has also been shown that the horizontal liquid spreading rate increases significantly after surface modification. In addition, a theoretical analysis of the spreading results indicates that this is due to the increase in the specific surface area of the surface-modified aerogels. Moreover, the spreading rate can be gradually tailored by changing the number of bilayers and the dimensions of the nanoparticles. Furthermore, we provide a new method to calculate the specific surface area of aerogel materials by combining the experimentally determined liquid spreading rate and a version of the well-known Kozeny–Carman equation.

Membranes and separators are crucial components in many processes and devices. The state-of-the-art fossil-based membranes have a high carbon footprint, and polyfluorinated membranes are increasingly phased out. These limitations lead to an inevitable transition that calls for carbon-neutral membranes with the same or even better performance that can be produced at scale and low cost. Cellulose membranes have the potential to fulfill these criteria if they can be tuned for different purposes. A way to tailor cellulose membranes by preparing them from cellulose fibrils of different refining degrees is presented. The membranes’ effective pore size and permeability to PEG, Fluorescein, and different ions were characterized. The membranes were efficiently used as separators in aqueous-based Zn-ion batteries and PEDOT supercapacitors. This work demonstrates a route toward high-performing and versatile cellulose membranes that can be produced at scale in a more sustainable membrane industry.

Research interest in quaternization of cellulose fibres has increased considerably over the past decades. However, there is little or no consensus regarding how to characterize the material in terms of degree of substitution (DS), and the literature suggests a range of different methods focusing on charge determination as well as nitrogen content quantification. This work aims to fill the knowledge gap regarding how the different methods perform in relation to each other, and for what cellulosic systems each method has advantages, disadvantages and even potential pitfalls. FT-IR and NMR measurements are used to establish successful modification and determine the relative number of substituent groups. Another six methods are compared for the determination of the DS of cellulosic fibres and nanofibrils. The methods include Kjeldahl measurements, nitrogen determination by chemiluminescence, determination of molecular nitrogen by the Dumas method, colloidal titration, conductometric titration and polyelectrolyte adsorption. It can be concluded that most techniques investigated are reliable within certain ranges of DS and/or when using appropriate post-treatment of the quaternized material and suitable sample preparation techniques. The results from the present work hence provide recommendations to make an educated choice of method, and experimental protocol, based on the technique at hand.

Plant cells represent smart cargo carriers with great socioeconomic potential in oral drug delivery applications. The two exterior barriers, featuring a rigid cell wall and a dense plasma membrane, are unique with complementary structural, mechanical, and chemical properties. Current strategies for producing therapeutic drugs within plant cells for oral delivery are efficient, but largely limited to recombinant pharmaceutical proteins, and involve complex genetic modification of plants. To address this, we engineer plant cell–inspired delivery systems with cellulose nanofiber–based shells and lipid layers through a bottom-up assembly strategy, which offers greater flexibility to encapsulate nonprotein compounds and nanoparticles. Notably, the layered shell structure resists degradation in acidic environments, and two barriers respond differently to external stimuli in simulated gastrointestinal medium, resulting in size-dependent dual-triggered release mechanisms. The cytocompatibility was shown by incubation with Caco-2 cells. Our results open avenues for developing next generation of bioinspired oral delivery systems for multisite-specific gastrointestinal release in a low-cost and sustainable manner.

Cellulosic nanomaterials are ideal reinforcers in hydrogel composites, but the current techniques that ensure defined nano-dimensions reduce sustainability. A different strategy for the synthesis of hydrogels from pulp fibers using green chemistry could offer a more sustainable solution. This work explores a mild, straightforward chemical modification with maleic anhydride that simultaneously decorates the fibers with carboxylate and alkene groups. Tuning the temperature of the reaction enables control over the surface charge ranging from 150 to 1,000 μmol/g. The fibers are used to construct a rubber-like, water-stable hydrogel composite prepared by in situ telechelic PEG polymerization followed by thermal or UV-induced free radical crosslinking. The initiation strategy, molecular weight of telechelic PEG, and degree of modification of the fibers enable control over the network formation within and around the fibers. The hydrogel composite is designed to be hydrolytically degradable under alkaline conditions, allowing separate recovery of both fibers and polymer precursors.